This invention relates to ultrasonic scanning apparatus.
The applicator of a mechanical ultrasonic, sector scanner, more particularly of one for ultrasonic tomographic examination of the human heart, should ideally be such that the sound head thereof can be moved at a presettable, more particularly constant, angular velocity. In addition, the course of the displacement, the image frequency and the maximum angle should be readily variable by electronic control. Also, it should be possible, more particularly for heart-phase-triggered individual-image photography, to run-up the sound head from a position of rest to a desired, more particularly constant, angular velocity in a minimum time. A further requirement is that the drive should always lie outside the liquid used, for example, as a lead path, and it should have a long useful life, while in addition it should be possible to change the sound head readily and rapidly. At the same time, it is desirable for the applicator always to be of small overall dimensions and compact, as well as being light and possibly bent over at an angle, so that it can be readily applied regardless of the position of the body. Driving systems are described, for example, in German Offenlegungsschrift Nos. 27 50 160, 22 16 577 , German Auslegeschrift No. 26 01 559, German Patentschrift No. 25 29 155, U.S. Pat. No. 4,034,744, and "Ultrasonics", July, 1978, pages 171 to 178. U.S. Pat. No. 4,106,492 also describes ultrasonic scanning apparatus. The ultrasonic scanning apparatus described in U.S. Pat. No. 4,106,492 only permits pivoting angles of the sound head in the range from 0.degree. to .+-.25.degree.. In the apparatus described therein there are compared with one another, by way of actual-value/desired-value comparison for the sound head angular position, two functions which differ appreciably from one another in configuration. Thus, a sine function occurring as an actual-value signal is compared with a triangular function occurring as a desired-value signal, which signals have equality of form only for small angles, i.e. in a very small signal range.